Energy-absorbing pads

ABSTRACT

An energy-absorbing pad structure includes an energy-absorbing pad that is encapsulated by a polymeric film. The polymeric film is sufficiently air-permeable to permit air to escape during rapid compression of the pad structure, such as from a high-speed dynamic impact, but nonetheless is water resistant under ordinary conditions. It is desirable that the polymeric film is made from an elastic polymer. The air-permeability can be provided from a series of perforations such that the film&#39;s elastic quality tends to contract the perforations thereby impeding the progress of water through them under normal conditions. The energy-absorbing pad can be a semi-rigid viscoelastic foam.

This application is a continuation of application Ser. No. 11/211,315filed Aug. 25, 2005 (now U.S. Pat. No. 8,039,078 issued Oct. 18, 2011),which application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/604,607 filed Aug. 26, 2004. The contents ofboth of these applications are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The invention relates generally to an energy-absorbing pad that isencapsulated by a sealed film, and more particularly to a viscoelasticenergy-absorbing foam pad encapsulated by a perforated polymer film.

DESCRIPTION OF RELATED ART

Polymeric protective foams (e.g. protective foam layers) are widely usedfor impact force attenuation in a variety of safety-relatedapplications. These include sport applications, military combatapplications, automotive applications, footwear applications, etc. Ingeneral, a protective foam layer is placed adjacent or against a part ofa person's body to protect a body part (e.g. a head) during an impact.

Protective foams function by absorbing and/or dissipating the impactenergy from the force of an impact. An energy absorbing foam deforms orcrushes on impact thereby consuming a portion of the impact energy toprevent its reaching the underlying body part. An energy dissipatingfoam also spreads the impact force over a larger surface area than theactual area of impact so the force per unit area is decreased for theunderlying body part compared to that for the initial impact surface(e.g. the outer surface of the protective layer or a hard outer shellover the protective layer).

Traditionally, rigid foam pads are used in safety-related applications,made from foams that are non-recovering (i.e., they do not recover orrebound to any significant degree once they have been crushed) and donot provide comfort to the user. Such foams are not viscoelastic, andtheir structure essentially is destroyed on impact. Therefore, it isdesirable to use semi-rigid protective foam pads that provide bothcomfort and energy-absorbing capabilities, and which are viscoelasticand recover (i.e. they re-expand to their pre-impacted shape) afterimpact.

Current energy-absorbing pads used in combat helmets can be made, e.g.,by encapsulating an acceleration rate sensitive material with anon-porous coating that traps air and to a degree prevents compressionof the coated foam. Such a design is the subject of U.S. Pat. No.6,467,099. However, this structure has several significantdisadvantages. First, the coating material used to cover the pads isboth expensive and difficult to apply. In order for the pad toeffectively attenuate an impact force, the coating must remainsubstantially continuous, non-porous and free from perforation. This canbe difficult to guarantee, especially during combat conditions whenrepeated impacts may be likely. Second, the coating is often a sprayedon solvent-based material, as in the preferred embodiment of U.S. Pat.No. 6,467,099, which provides minimal resistance to chemicals andsolvent-based products, such as insect repellants, acetone, etc. thatmay be encountered in the field. Third, the process of applying such asolvent-based coating involves specialized equipment to capture thesolvent vapors released when the coating is dried.

SUMMARY OF THE INVENTION

An energy-absorbing pad structure is provided, which has anenergy-absorbing viscoelastic foam pad and a perforated polymeric filmencapsulating the foam pad. The perforated polymeric film is resistantto water penetration.

An energy-absorbing pad structure also is provided, which has anenergy-absorbing viscoelastic foam pad and a polymeric film layerencapsulating the foam pad. The polymeric film layer is resistant towater penetration but sufficiently air permeable to permit air that isexpelled from the foam pad on rapid compression thereof to escapethrough the polymeric film layer to the ambient atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of an energy-absorbing padstructure 10 as herein described.

FIG. 2 shows a perspective view of the pad structure of FIG. 1,partially broken away to show the arrangement of layers thereof.

FIGS. 3 a-3 b show, schematically, a process for making the padstructure of FIG. 1.

FIG. 4 is a cross-sectional view of the pad structure of FIG. 1, butwith additional layers of energy absorbing material 40 provided inbetween the respective top and bottom portions of the polymeric film 3and the textile covering 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In the description that follows, when a preferred range such as 5 to 25(or 5-25) is given, this means preferably at least 5 and, separately andindependently, preferably not more than 25.

With reference to FIG. 1, there is shown an embodiment of a padstructure 10 contemplated herein. A polymeric film 3 encapsulates anenergy-absorbing pad 1, and a textile covering 4 encapsulates theenergy-absorbing pad 1 and the polymeric film 3. As more fully describedbelow the polymeric film 3 generally is provided as two opposing sheetsor portions of film that are joined together around the perimeter of thepad 1 at seam 5, as seen more clearly in FIG. 2. The textile covering 4likewise can be provided as two opposing sheets or portions that arejoined together around the perimeter of the pad 1 as shown. Anintermediate adhesive (shown schematically as layer 2, which has beenexaggerated in the figures for clarity) can be applied to the surface ofthe pad 1 to adhere the polymeric film 3 to the pad 1. Alternatively,the polymeric film 3 can be adhered to the foam pad 1 without anadhesive, e.g. via heat bonding the polymeric film 3 to the pad 1 asfurther explained below. It is understood that the arrangement shown inFIG. 1 can include additional materials or layers arranged intermediateor adjacent the layers or components thereof, e.g. between polymericfilm 3 and textile covering 4.

To facilitate the following description, there is defined a top surface12 of the energy absorbing pad 1, and a bottom surface 14 thereof. It isto be understood that there is not, necessarily, any physical differencebetween the opposite surfaces 12 and 14, as the pad can be made from afoam of substantially uniform composition. Rather, the distinction ismade herein merely to aid the following description, where the topsurface 12 in use will face away from the body part being protected (ahead), and the bottom surface 14 will face toward the body part beingprotected. Also as referenced herein, the opposing sheets or portions ofthe polymeric film 3 and of the textile covering 4 sometimes arereferred to, respectively, as top and bottom portions similarly as abovedepending on whether they are provided adjacent the top or bottomsurface 12 or 14 of the pad 1. Each of the materials and componentsdescribed above and shown in FIG. 1, as well as methods for providingand assembling them to provide the pad structure 10 shall now bedescribed.

The energy-absorbing pad 1 is a structure that can be placed over a bodypart in order to provide protection from an impact. One application ofparticular utility is to provide the pad structure 10 inside the outershell of a sports or combat helmet in order to provide protection to thewearer's head from a dynamic or ballistic impact to the helmet shell. Itis desirable that the pad 1 is compressible on impact to dissipate orconsume at least a portion of the impact force. It is also desirablethat the pad 1 be lightweight. Advantageously, the energy-absorbing pad1 is made from foam, preferably a viscoelastic foam, and even morepreferably a semi-rigid viscoelastic foam such as is disclosed inPublished PCT patent application No. PCT/US2004/034596 (published as WO2005/042611), which is incorporated herein by reference in its entirety.In one embodiment, the pad 1 can be made from a number of discrete foamlayers wherein individual layers of foam are joined or otherwiselaminated together to form the pad 1. The individual foam layers can bemade from different foams, and there can be 2, 3, 4, or more foam layersin the construction of the foam pad 1. In one desirable embodiment, thepad 1 is made as a two-layer structure having a layer of high-modulusfoam glued or joined to another layer of relatively low-modulus foam.

Foams are lightweight and typically are compressible on impact, capableto absorb or dissipate at least a portion of the impact energycommensurate with the particular foam's rigidity and viscoelasticity.Additionally, in their uncompressed state, foams have a significantproportion of their volume composed of air, which occupies the cellularstructure of the foam. The air within the foam provides an additionalmode of energy absorption on impact based on the gas compressibility ofair. Foams can be designed to be either open-celled or closed-celled inorder to take advantage of different aspects of foam rigidity versus airpermeability and entrapment within the cell structure to achievedifferent mechanisms of impact force attenuation as is understood in theart. The semi-rigid viscoelastic foam which is preferred for theenergy-absorbing pad 1, e.g. as disclosed in Publication No. WO2005/042611, can provide significant protection against dynamic impacts,such as from a ballistic impact against the outer shell of the helmet orother protective gear incorporating the pad structure 10, when situatedbetween the outer shell and the wearer.

For example, a semi-rigid viscoelastic polyurethane foam that is madefrom a significant proportion of propylene oxide-extended amine-basedpolyether polyols which contain substantially no ethylene oxideextension units, together with other filled and/or unfilled polyetherpolyol(s) as described in the aforementioned publication, as well asisocyanate (index 60-130) and appropriate catalysts, providessignificant high speed dynamic impact protection to a significant degreecomparable to rigid foams (e.g. expanded polystyrene). But such a foamnevertheless can be nondestructively deflected and will recover at adelayed rate following such deflection commensurate with the foam'sviscoelasticity (its hysteresis function). This is unlike conventionalrigid foams such as expanded polystyrene, which can provide adequateprotection against high speed impacts, but which are destructivelycrushed and cannot recover or be reused. In addition, being a semi-rigidfoam and not a rigid foam, the preferred foam for the pad 1 alsoprovides a measure of protection against low-speed or even static orquasi-static impact forces, which cannot be matched by rigid foams suchas expanded polystyrene. More specific details for such semi-rigidviscoelastic foams are provided in Publication WO 2005/042611,incorporated herein.

Alternatively, the energy-absorbing pad 1 can be comprised of amulti-impact closed-cell foam such as closed-cell polyethylene foam,Insulate™ foam, plasticized closed-cell vinyl foam, closed-cellpolypropylene foam, etc. These closed-cell foams are generally made inslab form and are blown or expanded into foam by an autoclave orextruder. In a further alternative, the energy absorbing pad 1 can beprovided from any suitable material or foam that is known orconventional in the art for providing dynamic impact protection,although it is desirable that the material for pad 1 not be a rigid foamsuch as expanded polystyrene that will not recover following destructivedeflection or “crush” on impact.

The shape of the energy-absorbing pad 1 will depend on the particularapplication and may be, e.g., a rectangle, circle, trapezoid, etc.,comprising a thickness of typically about or less than 2 inches for mostbody protecting applications. It is desirable that the shape of the pad1 fit easily into a protective shell such as a helmet shell or othershell used in the various applications discussed below. In oneembodiment, the pad 1 is approximately 3⅜ inches in length, 2 inches inwidth and ¾ of an inch in thickness. However, it is understood that thepad 1 can be any shape and should not be limited to the applicationsdiscussed herein.

The energy-absorbing pad 1 is capable of absorbing and/or dissipating atleast a portion of the energy of an impact. As noted above, a semi-rigidviscoelastic foam, desirably used for the pad 1, will providesignificant protection against a high speed dynamic impact due to itssubstantial rigidity, but it also will recover and retain its rigidityfollowing such impact so it may be reused. The compression andhysteretic (due to its viscoelastic structure) characteristics of such afoam dampen and disperse the force of a high-speed impact. The abilityof pad 1 to recover after impact also gives it long-term use anddurability, which is desired in athletic and combat equipment.

A viscoelastic foam used for the pad 1 desirably will recover within thefollowing guidelines following the referenced degree of compression: Thetime for the energy-absorbing pad 1 to substantially recover from acompression of 50% its original height is in the range of 3 seconds to120 seconds. Substantial recovery of the energy-absorbing pad meansrecovery to at least 85, preferably 90, preferably 95, percent of theinitial pre-compressed height following compression thereof. Further, itis desirable the pad 1 can recover from such a 50% compression to 80% ofits pre-compressed height in the range of 2 seconds to 60 seconds,preferably 3 seconds to 30 seconds, and more preferably about 3 secondsto about 20 seconds. Following a 75% compression from its originalheight, the pad 1 should substantially recover in the range of 4 secondsto 240 seconds, and should recover to 80% of its pre-compressed heightin the range of 3 seconds to 120 seconds, preferably 3 seconds to 90seconds, and more preferably about 3 seconds to about 60 seconds.

The polymeric film 3 can be an elastic and flexible film as known in theart, preferably that is capable of being fused or fusion bonded to formthe seam 5 as described below. The polymeric film 3 can be anyconventional or known polymeric film, such as a polyolefin film (e.g.polyethylene and/or polypropylene), polystyrene, polyester, urethane,polyurethane, aliphatic polyurethane, etc. The polymeric film 3 can alsobe made from any of the other well-known natural polymers such ascellulosic materials and/or other biopolymers (e.g. polylactic acid).

Suitable film materials are available from Deerfield Urethane, Inc.,South Deerfield, Mass., as Dureflex™ PT 9400S or Dureflex™ PT 6100S,which are flexible and elastic polyurethane films. These products areproprietary polyurethane films that have tear resistance greater than500 pli, tensile strengths greater than 8000 psi and ultimateelongations greater than 500%. Other flexible polyurethane films alsomay be suitable for the polymeric film 3 herein, e.g., otherpolyurethane films available from Deerfield Urethane, Inc., StevensUrethane, Easthampton, Mass., or from other commercial sources.

As noted above, Dureflex™ PT 9400S and Dureflex™ PT6100S are proprietarycompositions. The major component of these films is a polyurethanepolyether elastomer.

The polymeric film 3 encapsulates the energy-absorbing pad 1 to providea durable, water and chemical resistant barrier around the pad 1. Thepolymeric film 3 prevents or substantially impedes the flow of liquidssuch as water to prevent or impede them from absorbing or penetratinginto the energy-absorbing pad 1. For example, the polymeric film 3shields the pad 1 from the wearer and thereby prevents the pad 1 fromabsorbing the perspiration generated by him/her, which otherwise may beabsorbed by the pad 1, particularly if the pad is made from a cellularmaterial such as foam. A pad 1 that has been saturated with water orperspiration is undesirable to a user because of the increased weight ofthe pad 1 and the overall reduction in comfort to the wearer. Inaddition, moisture in the pad 1 may adversely affect the pad's abilityto absorb and/or dissipate energy from the force of an impact. Forexample, in the case of a viscoelastic foam the presence of moisture mayalter the hysteresis function for the foam causing it to dissipateenergy differently or to a different or lesser extent than the dry foam.

In addition to providing a barrier that is resistant to waterpenetration, it is desirable that the polymeric film 3 also providesmeans for the discharge of air that is expelled from the foam's cellularstructure upon an impact-induced compression of the foam pad 1. That is,the polymeric film 3 should be resistant to water penetration underordinary conditions, but be or become sufficiently air permeable on adynamic or ballistic impact or similar compression event to permit airexpelled from the foam pad's cellular structure on compression thereofto escape the polymeric film 3. Otherwise, excess ballooning of thepolymer film 3 also may adversely affect the energy-absorbing impactattenuation characteristics of pad 1. To provide the desired airpermeability, the polymeric film 3 is perforated to provide a passage orpassages through the film 3 for air that is expelled from theenergy-absorbing pad 1 on impact to escape. The perforations (shownschematically at 8) also allow the passage of air from the outsideenvironment back into the pad 1 so the pad 1 can recover (i.e. expand ordecompress to its original pre-impact shape) after the impact load isremoved. Advantageously, the perforations 8 are designed so that they donot permit liquids such as water to penetrate the film 3 from theoutside environment under normal conditions.

It is also desirable that the perforations 8 provide some measure of airpermeability through the film 3 even under non-impact conditions, suchas due to changes in the ambient air pressure as may be encountered whenclimbing or descending in an airplane. Otherwise, if air were notpermitted to escape the pad structure 10 through the perforations 8, thefilm 3 would tend to balloon on climbing as the ambient pressuredecreased (or to shrink on descending as ambient pressure increased) inorder to maintain constant pressure across the film 3. Because air issignificantly less dense than water, the perforations 8 inherently willpermit air to flow therethrough to a significantly greater degree thanwater, which in part is how the perforations present a desired degree ofair permeability but nevertheless are able to maintain adequatewater-penetration resistance. Thus, it will be recognized that whilesufficiently small perforations can be provided through the film 3 so asto substantially inhibit or prevent the passage of water under normalconditions, they advantageously will permit the passage of air inresponse to a pressure gradient across the film 3.

The substantially water-impermeable but air-permeable (at least duringan impact) behavior of the perforations 8 provided in the polymeric film3 can be understood and provided as follows. When very smallperforations are made, e.g. using a needle point of very small diametersuch as around 0.005 inches, the resulting perforations 8 are verysmall. The elastic character of the film 3 also will prevent expansionof the perforations 8 sufficiently so they do not substantially admitdroplets of water, at least not from incidental water contact such asrain, and even under modest or moderate conditions of hydrostaticpressure, such as immersion within six inches or one foot of water, ormore. However, on a dynamic compression event such as from a ballisticimpact, the air expelled from the encapsulated foam pad 3 induces apressure gradient across the film 3 relative to ambient atmosphericpressure, such that the perforations 8 expand against the elastictendency of the film 3 to permit the air to escape, thus equalizing thepressure across the film 3. Once the impact load has been removed, thefoam pad 1 will tend to return to its pre-compression shape based on itsown viscoelastic character, thus generating a pressure gradient in theopposite direction across the film 3 to draw air back into the foam'scellular structure as it is re-expanding. Thus the foam's own tendencyto re-expand induces a pressure gradient across the film 3 sufficient todraw air back in and re-fill the foam's cellular structure of air.

Without perforations, the polymeric film 3 still may exhibit a measureof inherent gas (i.e. air) permeability based the material's porosity,but not enough to permit sufficient air passage through the film onrapid compression of the pad to avoid splitting the sealed seam 5(discussed below) between the opposing sheets or portions of thepolymeric film 3. (It should be evident that the inherentgas-permeability of a polymeric film, as a material property based onthe film's porosity, is not the air-permeability that is referred toherein; air-permeability herein refers to a substantial measure of airpenetrability through a polymeric film 3 resulting from perforations 8).Furthermore, even if the seam 5 held, the rate of gas diffusion throughthe non-perforated polymeric film 3 would be so minimal that airexpelled from the energy-absorbing pad 1 on rapid compression would belargely trapped by the film 3 causing it to balloon, and may preventsuitable physical compression or deformation of the pad 1 thus impedingor counteracting the pad's 1 energy-absorptive function. As a result,the desirable viscoelastic characteristics of the energy-absorbing pad 1may be largely negated because of the trapped air in the non-perforatedpolymeric film 3.

The perforations can be made with a needle point, preferably having abeveled point or end. The diameter of the needle point that penetratesthe film 3 should be 0.001″ to 0.01″, preferably about 0.003″ to about0.008″ and more preferably about 0.005″. The perforations can be made bypassing the needle from the outside surface of the polymeric film 3through the film 3 towards the pad 1. In this embodiment, the film 3 canbe assembled to the pad 1 and then perforated, wherein the needlepoint(s) may extend somewhat into the underlying foam pad to a smalldegree before being withdrawn. This should not adversely affect thepad's function or structure. Otherwise, the perforations can be made bypassing the needle from the pad 1 side of the polymeric film 3 throughthe film towards the outside, which would require the film 3 to beperforated prior to being assembled to the pad 1.

It is preferred that the number of perforations in the polymeric film 3is sufficient to allow the discharge of air upon a high speed impact asdescribed above. The perforations are preferably spaced apart in orderto form a grid pattern or array of perforations in the polymeric film 3.Accordingly, it is preferred that the spacing between adjacentperforations is in the range of 0.05-1, preferably 0.05-0.5, preferably0.1-0.25, inches, and that the perforations are provided in a regulararray of uniformly spaced perforations. To provide such an array ofperforations, a corresponding array of needle points can be provided ina jig that is then pressed against the surface of the polymeric film 3at an appropriate location such that the needle points are caused topenetrate the film 3 to provide the perforations. To further ensure thatthe elastic tendency of the film 3 will tend to hold the perforationsclosed against water penetration under ordinary conditions, it may bedesirable to stretch the polymeric film 3 a small degree, such as atleast or about 1, 2, 3, 4, or 5, percent, or greater (such as at least10, 15 or 20 percent), so that the film is in a stretched condition whenthe perforations are made. Then, following perforation of the film 3 itis allowed to relax back to its original un-stretched condition, and isprovided to encapsulate the foam pad 1 in its un-stretched condition. Asa result, the elasticity of the polymeric film 3 will strongly tend tocontract the perforations under normal conditions, and even against amodest or potentially a moderate pressure gradient. However, on rapid orballistic compression of the foam pad 1 encapsulated within thepolymeric film 3, air is expelled from the foam at a sufficient rate sothat the resulting pressure gradient counteracts the contractiletendency of the film 3 so that the air can escape through theperforations.

In one embodiment, only the top portion of the encapsulating polymericfilm 3 (facing away from the user's body in use) is perforated.Alternatively, both the top and bottom portions can be perforated, oronly the bottom portion.

In a further embodiment, the top and/or bottom portion(s) of thepolymeric film 3 can consist of one ply or of multiple plies ofpolymeric film material. For example, the top portion of the polymericfilm, overlying the entire top surface 12 of the energy-absorbing pad 1,can be one or more plies of polymeric film material. The bottom portionof the film 3 overlying the entire bottom surface 14 also can besimilarly provided having one or more plies of polymeric film material.Multiple plies of polymeric film material can be used to achieve anoverall thickness for the polymeric film 3 that is desired in a givenapplication, and/or to control or regulate the rate of air expulsionfrom a dynamic impact event based on empirical testing. For example, thetop portion of the polymeric film 3 can include a plurality of plies orlayers of polymeric material, while the bottom portion of the polymericfilm is provided having only one layer or ply. In this embodiment, it isdesirable that only the top portion (consisting of a plurality, such asthree, plies) be perforated, while the single-ply bottom portion of thepolymeric film 3 remains non-perforated.

The thickness of the top portion of the polymeric film 3 can be madegreater than that of the bottom portion thereof, either by using moreplies for the top portion as described above, or by using a thicker filmfor the top portion than for the bottom portion. In one embodiment, thetop portion of the polymeric film 3 has a thickness in the range of 2mils to 15 mils, preferably from 2 mils to 10 mils, and more preferablyfrom about 2 mils to about 5 mils, and the bottom portion has athickness in the range of 1 mils to 15 mils, preferably from 1 mils to10 mils, and more preferably from about 1 mils to about 5 mils.

Optionally an intermediate adhesive layer 2 (shown exaggerated in thefigures) can be applied to the surfaces 12 and/or 14 of the pad 1 toadhere the opposing portions or sheets of the encapsulating polymericfilm 3 thereto. The adhesive layer 2 is applied to the surface of theenergy-absorbing pad 1, and adheres the polymeric film 3 to the pad 1thereby helping to prevent the polymeric film 3 from crinkling, shiftingor sliding over the surface of the pad 1 during use. The intermediateadhesive layer 2 can comprise, but is not limited to, an adhesive pasteor cement, adhesive fusible webbing or a no-sew bond fabric as known inthe textile and crafts arts. If it is a webbing or bond fabric, theintermediate adhesive layer 2 can be attached or held onto the surfaceof the energy-absorbing pad 1 by a semi-liquid or a gel material,Vaseline, grease, oil or glycerin, prior to affixing the polymeric film3 sheet. In the alternative, the intermediate adhesive layer 2 candirectly overlie the surface of the energy-absorbing pad 1 without anintermediate semi-liquid or gel. Furthermore, the intermediate adhesivelayer 2 can be applied to the surface of the energy-absorbing pad 1 byany conventional method known in the art.

In a further embodiment, the polymeric film 3 can be adhered directly tothe surface of the pad 1 via heat bonding, with no intermediate adhesivelayer. In this method, the polymeric film 3 (such as a polyurethanefilm) is heated to just above its softening point (or melting point) andbrought into contact with the surface of the foam pad 1 before it isthen allowed to cool back down to ambient temperature. The result isthat the polymeric film 3 is heat-bonded to the surface of the foam pad1 by being melded thereto in the softened or partially melted statebefore being cooled to re-solidify the film 3. Methods for heat-bondingpolymeric films to various substrates are known in the art, and will notbe further described here.

The textile covering 4 also can be considered optional. This covering 4is provided to encapsulate the polymeric film 3 and provide comfort tothe wearer, as well as in some applications a means for securing the padstructure 10 to the inner surface of an outer shell for protective gear.For example, at least the top portion of the textile covering 4 can beprovided as a high-pile fabric that can be secured to the inner surfaceof a protective shell, such as a helmet or kneepad shell, via ahook-and-pile fastener mechanism such as Velcro. In addition, the bottomportion of the textile covering 4 can be provided from a sewn or porousfabric material that is effective to absorb and wick moisture, such asperspiration, away from the wearer's underlying body part that may be incontact with the bottom portion of the textile covering 4 during use.

In one desirable embodiment, the bottom portion of the textile covering4 is composed of a material capable of wicking moisture away from asurface as described above, and the top portion of the textile covering4 is a fabric of sufficient pile to be readily retained by “hook”fasteners extending from the surface to which the pad structure 10 is tobe adhered, such as a pile fabric of a conventional Velcro or similarfastening system. For example, in this manner the pad structure 10 canbe easily secured to the inside of a protective shell for a helmet wherethe “hook” fabric has been previously attached or adhered. The textilecovering 4 can also be comprised of any fabric, woven material ortextile material conventionally known in the art, and can be providedfor any one or all of the foregoing purposes, in addition to any one orall of the following: aesthetic appearance, comfort, marketability ormerchandisability, printability, etc.

It is preferred, though not required, that the textile covering 4 is notphysically bonded to the polymeric film 3 over a significant portion oftheir respective surfaces in the pad structure 10. That is, the twomaterials 3, 4 are not laminated together. In the alternative, thepolymeric film 3 can be laminated, e.g. by heat or flame techniques, tothe textile covering 4.

In the embodiment illustrated in FIG. 2, the polymeric film 3 isprovided by joining top and bottom portions of polymeric film materialaround the perimeter of the energy-absorbing pad 1 to form a seam 5therearound. Also in that embodiment, the top and bottom portions of thetextile covering 4 also are joined together at the seam 5 to provide theillustrated structure, wherein the pad 1 is encapsulated within thepolymeric film 3, which is encapsulated within the textile covering 4.This construction can be made as follows.

A method for producing an energy absorbing pad structure 10 isillustrated schematically in FIG. 3. First referring to FIG. 3 a, theenergy-absorbing pad 1 is positioned having a first web of polymericfilm material 22 overlying the top surface 12 and a second web ofpolymeric film material 24 underlying the bottom surface 14 of the pad1. It is to be noted that reference here to “top” and “bottom” as wellas “first” and “second” is merely for convenience; the pad 1 might justas easily be oriented vertically during assembly instead of horizontallyas illustrated, in which case the first and second webs 22 and 24 mightbe referred to as “left” and “right,” respectively. Continuing, a firsttextile material web 26 is positioned above the first polymeric filmmaterial web 22, opposite the pad 1, and a second textile material web28 is positioned below the second polymeric film material web 24,opposite the pad 1.

A sealing die 30 is provided having opposed reciprocating membersoppositely provided over and under, respectively, the first and secondtextile and polymeric webs (22-28) with the pad 1 located centrallyin-between as shown. The reciprocating members have cooperatingdie-pressing faces 32 which are arranged such that when thereciprocating members are closed, the opposing faces 32 are pressedtogether along a pathway around the perimeter of the energy-absorbingpad 1 as seen in FIG. 3 b.

When the members of the sealing die 30 are closed (FIG. 3 b), the fourwebs (first and second polymeric film and textile webs 22-28) arepressed together along the pathway of the die-pressing surfaces 32. Thedie members are equipped to heat the portions of the webs in contactwith the die-pressing surfaces 32 around the perimeter of the pad 1 suchthat polymeric material webs 22 and 24 are caused to at least partiallysoften or melt, thus being joined together to form the seam 5 shown inFIG. 2 and as will be understood by those of ordinary skill in the art.Simultaneously, the textile material webs 26 and 28, which are incontact with the softened/melted portions of the polymeric webs alongthe pathway of the contacting surfaces 32, are permeated with and absorba portion of the polymeric material such that when that materialre-hardens or solidifies, the effect is to join all four webs at theseam 5 as will be understood.

For convenience, the process of FIG. 3 is illustrated schematically onlyfor a single pad 1. However, it will be understood to persons havingordinary skill in the art that a plurality, such as an array, of pads 1could be arranged in a die having a cookie-cutter die-pressing surface32 pattern designed to accommodate an array of pads 1. Subsequent to theheat-sealing step, the die members can be opened and the newly made padstructure 10 (or array of such structures 10) can be conveyed to adie-cutting station (not shown) where a cutting die can be used to freeeach pad structure 10 from the extraneous material webs by stamping.

In addition to heat-sealing using conventional heating methods, theenergy to soften or melt the polymeric webs 22 and 24 can be suppliedvia a radio frequency method. In such a method, the reciprocatingmembers of the die 30 are closed around the pad 1 along a pathway incontact with the material webs as before, and a radio frequency isapplied to the die, thereby transmitting radio waves through thepolymeric film material webs 22 and 24 as they are compressed togetheraround the perimeter of the pad 1. The radio waves excite the moleculesof the polymeric film sheets to generate sufficient heat to effectivelysoften or melt or seal (i.e. physically bond the layers together) thecompressed polymeric film material webs together to form the polymericfilm layer 3 around the pad 1. The methods and machinery for carryingout radio frequency sealing are known or conventional in the art. Aperson having ordinary skill in the art could make the selection ofappropriate devices and radio frequencies for a particular polymericfilm. In the alternative, other conventional heating methods can be usedfor applying heat to the polymeric sheets compressed in the die.

In a further alternative embodiment (not illustrated), the textilecovering 4 can be provided around the polymeric film 3 by sewing orotherwise sealing the opposing textile fabric layers or webs togetherseparately from the seam 5 made between the opposing polymeric filmmaterial webs.

In a still further alternative embodiment, the polymeric film 3 can beprovided by sewing the opposing polymeric film material webs together toprovide the seam 5 around the energy-absorbing pad 1. In thisconstruction, the seam 5 of the polymeric film 3 will not be air tight,and will include small openings between the opposing film portions whichmay provide sufficient air permeability to obviate the need of theperforations 8 discussed above. It is contemplated, however, that thepolymeric film sheets could be sewn together sufficiently tightly, orusing a small enough stitch that the polymeric film 3 still wouldpresent adequate water impermeability under most ordinary conditionswhere water may be encountered. Sewing together the polymeric filmportions may be less desirable because of the increased productioncosts. Furthermore, sewing together the polymeric film sheets may beless reliable than other methods as those described above.

Other alternatives for sealing or bonding the polymeric film sheetstogether can include gluing to create the desired seam 5. Conventionalglues or epoxy sealants well known in the art can be used to seal orbond the top and bottom polymeric film portions together to form seam 5.

The energy-absorbing pad 1 can be a foam that is formed integrally tothe polymeric film layer 3. In this embodiment, the pad 1 can beprepared by molding a foam in a mold wherein polymeric film material hasbeen used to coat the interior wall surfaces of the molding chamber. Asthe foaming composition (mixture of polyols and isocyanate for apolyurethane foam) rises or foams, it will come into contact with thepolymeric film material coating or lining the interior walls of themold. The foam is permitted to cure such that it cures and formsdirectly to the polymeric film material so that the resultingconstruction is of pad 1 having an integrally formed polymeric film 3directly on the surface thereof.

In another embodiment, the polymeric film 3 can be provided onto thesurface of the energy-absorbing pad 1 as a chemically deposited layerthat is applied directly on the surface of the pad 1 and then allowed orcaused to dry or cure to form a water resistant polymeric film. Thechemically deposited layer can be provided as an elastomeric coatingmaterial that is not yet cured. The elastomeric material can be athermoset powder coating composition that cures when exposed to heat,less preferably to a combination of heat and radiation. The elastomericmaterial can be deposited on the pad 1 by any of the well-known orconventional methods such as spraying, brushing, dipping, etc.,depending on the state and the viscosity (atomizability) of the coatingmaterial. The elastomeric coating can be sprayed on the pad 1 as athermoset solvent-release liquid or a thermoset powder. Once theelastomeric coating material is applied over the pad 1, it is heated toa temperature sufficient to cure and crosslink the elastomer. Oncecured, the elastomeric material effectively encapsulates the pad 1 as acoating on its surface.

It will be understood that in many of the above-described alternativemodes of applying a polymeric film 3, it may be necessary to perforatethat film to provide the perforations 8 after the film 3 has been formedaround or onto the pad 1 to provide the desired air-permeability.

It will be further understood that if the polymeric film 3 is to consistof multiple plies of polymeric material on one or both sides of the pad1, it may be necessary to adjust the heating/radio frequency time forone of the heat-sealing modes, or otherwise to take this intoconsideration when effecting a seal such as a seam 5 or other closuremethod such as sewing.

Optionally, as shown in FIG. 4 an additional layer of energy-absorbingmaterial 40 can be positioned adjacent the top and/or bottom surface(s)12 and/or 14 of the pad 1 in between the associated portions of thepolymeric film and textile covering layers 3 and 4. Such a layer(s) ifpresent can be made from the semi-rigid viscoelastic foam describedabove for the pad 1, and may provide an additional impediment to thepenetration of moisture into the main energy absorbing pad 1, e.g. inthe unlikely event of a submersion of extended duration or significantdepth. In addition, when placed adjacent the bottom surface 14 of thepad 1, such additional foam layer may provide additional comfort orcushioning benefits to the wearer, particularly when used in a helmetthat is worn for extended periods. In this embodiment, however, when thelayer 40 is intended as a comfort foam to be positioned adjacent thebottom surface 14 of the pad 1, it may be preferable to use a soft,flexible foam instead of a semi-rigid viscoelastic foam for the layer40.

The pad structure 10 described herein can be used in variousapplications and protective gear including, but not limited to, safetyequipment, combat helmets, athletic helmets, sporting equipment,kneepads, elbow pads, etc. Because the pad structure 10 effectivelyabsorbs the force on an impact, its use can be applied broadly to anyapplication in which it is desirable to protect body parts or equipment,such as electronics, tools, etc. It is even contemplated the padstructures described herein can be used as packing materials forshipment of goods where it is desired to provide protection against ahigh-speed dynamic impact while in transit.

Further aspects of the invention will become evident through referenceto the following example, which is provided by way of illustration andnot limitation.

Example

A semi-rigid viscoelastic foam pad measuring nominally 3⅜″×2″×¾″ wasencapsulated within a polyurethane film having nominally the samedimensions as applied. The polyurethane film was composed of Dureflex™PT9400S supplied by on one side of the foam pad, and Dureflex™ PT6100Son the other side, which films were joined together around the perimeterof the pad as further explained below. The encapsulated pad was furtherenclosed within a textile covering, one side of which was made from apile fabric similar to a Velcro and the other side of which was madefrom a wicking fabric such as a cotton fabric. To prepare thisconstruction, one ply of Dureflex™ PT9400S polyurethane film, 5 milthick, one ply of Dureflex™ PT6100S, 2 mils thick, one ply of Velcropile fabric and one ply of wicking fabric were die cut to oversizeddimensions relative to the pad. The polyurethane film, Velcro andwicking fabric sheets then were then perforated using a 0.005″ diameterbeveled-point needle. The perforations were made by penetrating in thedirection from the surface that was to face away from the pad, throughthe layers and toward the surface that was to face the pad. Theperforations were spaced about ½″ apart in the layers.

Then the layers were arranged with the foam pad in a die cavity asfollows: the wicking fabric was positioned in the bottom of the diecavity, one ply of 2 mil thick polyurethane film was placed on top ofthe wicking fabric, the pad was placed on top of the first ply ofpolyurethane film, one ply of 5 mil thick polyurethane film were placedon top of the pad, and the Velcro pile fabric was placed on top of theconstruction. A radio frequency was applied to the die, and then the diewas clamped shut around the layered construction similarly asillustrated in FIG. 3 b to compress the plies of polyurethane film, thewicking fabric and the Velcro fabric together along a pathway around theperimeter of the foam pad. The compressed layers were heated via theradio frequency for a period of up to 5 seconds to create an airtightseal around the perimeter of the pad. The resulting pad structure wasremoved from the die and extraneous material outside the newly formedseal was cut away.

The encapsulated pad (with the fabric removed) was then weighed to thenearest 0.01 gram prior to being submerged to a depth of six inches in a25° C. water bath. The encapsulated pad was submerged for a period of 24hours, after which the encapsulated pad was removed from the water bathand towel dried. The encapsulated pad was then placed on a rack to dryat ambient temperature for 24 hours. After drying, the pads were weighedto the nearest 0.01 gram. The initial weight was deducted from the finalweight to determine the weight of water absorbed by the pad. The finalweight of the pad was less than 1% greater then that initially measured(i.e. prior to submerging in the water bath). Hence, the perforations inthe polymeric film plies did not substantially adversely affect thewater impenetrability of that film measured according to the conditionsof the test, which were intended to be more stringent (in terms of watercontact) than a typical piece of protective gear might encounter inordinary sport or combat applications

Although the above-described embodiments constitute the preferredembodiments, it will be understood that various changes or modificationscan be made thereto without departing from the spirit and the scope ofthe present invention as set forth in the appended claims.

1. An energy-absorbing pad structure comprising an energy-absorbingviscoelastic foam pad, and a polymeric film encapsulating said foam pad,said polymeric film containing perforations that inhibit or preventliquid water from passing through said polymeric film into said foam padin the absence of a pressure gradient across the film, but which permitair to pass through said polymeric film out of said foam pad when thepad structure is subjected to a compression event and to pass throughsaid polymeric film into said foam pad following said compression event,said foam pad having a pre-compression shape before the compressionevent, whereby the foam pad can recover to the pre-compression shapefollowing the compression event, said polymeric film being made from awaterproof elastic polymer, wherein the polymer's elasticity contractsthe perforations in the polymeric film to resist water penetrationthrough said film.
 2. A pad structure according to claim 1, said elasticpolymer being an elastic polyurethane.
 3. A pad structure according toclaim 1, said foam pad having opposite first and second surfaces, saidpolymeric film comprising a first portion of polymeric film materialapplied over said first surface, and a second portion of polymeric filmmaterial applied over said second surface, said first and secondportions of polymeric film material being joined together at a seamaround the perimeter of said foam pad.
 4. A pad structure according toclaim 3, said first and second portions of said polymeric film beingjoined at said seam by heat-sealing or radio-frequency sealing.
 5. A padstructure according to claim 3, said first and second portions of saidpolymeric film being joined at said seam by sewing.
 6. A pad structureaccording to claim 3, wherein only one of said first and said secondportions of polymeric film material is provided with perforations.
 7. Apad structure according to claim 3, said first portion of said polymericfilm being thicker than said second portion of said polymeric film.
 8. Apad structure according to claim 3, said first portion of said polymericfilm comprising a plurality of polymeric film plies overlying the entirefirst surface and at least one more ply than said second portion of saidpolymeric film overlying the entire second surface.
 9. A pad structureaccording to claim 1, said polymer film being bonded to the foam pad.10. A pad structure according to claim 9, said polymer film being bondedto the foam pad via an intermediate adhesive layer.
 11. A pad structureaccording to claim 1, said viscoelastic foam pad being made from asemi-rigid viscoelastic foam.
 12. A pad structure according to claim 11,said semi-rigid viscoelastic foam being formulated from a polyolcomposition comprising at least one propylene oxide-extended amine-basedpolyether polyol that has substantially no ethylene oxide extensionunits, and at least one filled or unfilled non-amine-based polyetherpolyol, said polyol composition being combined with an isocyanatecomposition at an index of 60-130 to provide said semi-rigidviscoelastic foam.
 13. A pad structure according to claim 11, whereinafter compression of said semi-rigid viscoelastic foam to 50% itsoriginal height, said foam substantially recovers to its initial shapein from 3 to 120 seconds.
 14. A pad structure according to claim 1,wherein the foam pad measuring nominally 3⅜″×2″×¾″, and saidencapsulating polymeric film having nominally the same dimensions, andwherein the polymeric film allows less than one percent by weight ofwater, compared to the initial weight of the foam pad and the polymericfilm, to enter the foam pad through said perforations followingsubmersion of the pad structure in six inches of water for 24 hours. 15.A pad structure according to claim 1, further comprising a layer ofenergy-absorbing foam disposed adjacent said polymeric film.
 16. A padstructure according to claim 1, further comprising a layer of soft,flexible foam disposed adjacent said polymeric film.
 17. A pad structureaccording to claim 1, said foam pad comprising a first layer of foamjoined to a second layer of foam, the foam of the first layer has ahigher modulus than the foam of the second layer.
 18. A pad structureaccording to claim 3, said foam pad comprising a first layer of foamjoined to a second layer of foam, the foam of the first layer has ahigher modulus than the foam of the second layer.
 19. A helmetcomprising a helmet shell and a pad structure according to claim 1secured to an inner surface of the helmet shell.
 20. A helmet accordingto claim 19, further comprising a plurality of said pad structuressecured to said inner surface of said helmet shell.
 21. A pad structureaccording to claim 1, said foam pad being an open-cell foam.
 22. Ahelmet according to claim 19, said foam pad being an open-cell foam. 23.A helmet according to claim 19, said foam pad comprising a first layerof foam joined to a second layer of foam, the foam of the first layerhas a higher modulus than the foam of the second layer.